Hepatitis C Update Laboratory Issues Hema Kapoor MD

Hepatitis C –Update Laboratory Issues Hema Kapoor MD. SM Virology Section Manager Bureau of Laboratories Michigan Department of Community Health 6/03/03 1

Laboratory Tests for HCV Available at MDCH ØScreening tests EIA ØSupplemental RIBA ( Recombinant immunoblot assay) Nucleic acid Amplification tests 6/03/03 Additional Tests Available Commercially ØCIA (Chemiluminescence's immunoassays) ØQuantitative RNA Tests ØGenotyping ØCore Protein Antigen 2

Laboratory Algorithm for HCV Testing Negatives Screening Test for Anti-HCV* REPORT Positive EIA/CIA Test OR RIBA for anti-HCV Nucleic acid test for HCV RNA Negative Positive REPORT Negative Indeterminate REPORT Positive REPORT RIBA for anti-HCV Positive REPORT Negative REPORT Indeterminate REPORT * HCV EIA 2. 0 ( Abbott), HCV version 3. 0 ELISA( Ortho), VITROS Anti-HCV 6/03/03 3

Anti-HCV EIA False Positivity* by Population Prevalence Percent False Positive 100 6/03/03 HCWs Military STD Clients Pregnant Women 50 Dialysis Transfused 0 <5% Injecting Drug Users NANB Hepatitis ALT 10% 60% >90% Prevalence of HCV Infection * As judged by RIBA or NAT Source: CDC 4

CDC 6/03/03 5

Consistency of Reported Anti-HCV Results Ø Ø Screening test positive signal to cutoff ratios* Results above the cutoff should predict a true antibody positive Ø Only results below the cutoff would require supplemental antibody testing Ø Cutoff should perform the same regardless of the population being tested * Not intended for use in screening donors as provided by FDA guidance 6/03/03 6

Anti-HCV Test Versions Evaluated Ortho 3. 0, RIBA 3. 0 Abbott 2. 0, RIBA 3. 0 N=8, 754 N=25, 532 v STD patients v High-risk v Students v Hemodialysis patients v STD patients v HCWs v General population (NHANES IV) VITROS Anti-HCV (Ortho), RIBA 3. 0 N=1326 v Clinical specimens (Hospital-based patients) v Low prevalence populations 6/03/03 7

EIA Signal to Cutoff Ratio ØSignal: Optical density (OD) value of the sample being tested. ØCut off: Mean absorbance of negative Control plus 0. 600. Example: Sample OD 1. 595 1. 243 1. 271 Cutoff OD 0. 623 0. 543 S/CO 2. 56 2. 29 2. 34 s/cut off (s/co)- 3. 8 6/03/03 8

Proportion of Anti-HCV EIA* Screening Test Positive Results Testing RIBA Positive by Average S/Co Ratio Prevalence 4. 3% 2. 2% 0% _ * EIA 2. 0 or EIA 3. 0 6/03/03 Source: CDC. MMWR 2003; 52 (No. RR-3). 9

Proportion of Anti-HCV CIA* Screening Test Positive Results Testing RIBA Positive by S/Co Ratio Prevalence > (n = 1184) (n = 142) Screening-test-positive s/co ratio * VITROS Anti-HCV assay 6/03/03 Source: CDC. MMWR 2003; 52 (No. RR-3). 10

Proportion of Anti-HCV EIA RR Results Requiring RIBA Based on S/CO Ratio <3. 8 and HCV Prevalence Source: CDC. MMWR 2003; 52 (No. RR-3). 6/03/03 11

Use of EIA/CIA S/CO Ratio to Determine Need for Additional Routine Testing Ø Screening-test-positive samples with s/co ratios >3. 8*/8† can be reported based on screening test Ø Ø Screening-test-positive samples with s/co <3. 8*/8† require additional testing because most are falsely positive. Ø Ø >95% will be RIBA positive. In high prevalence populations few in this range. Limits cost while improving accuracy of reported results. 6/03/03 * Applies only to Ortho 3. 0 or Abbott 2. 0 EIA † Applies only to Ortho Vitros CIA 12

Laboratory Algorithm for Anti-HCV Testing and Result Reporting: MMWR 2003 Negatives Screening Test for Anti-HCV REPORT OR Positives defined by s/co ratios* All positives Positives with low s/co ratios Positives with high s/co ratios OR REPORT Nucleic acid test for HCV RNA RIBA for anti-HCV Positive Negative Indeterminate Positive REPORT RIBA for anti-HCV Positive REPORT Negative REPORT Indeterminate REPORT * HCV EIA 2. 0( Abbott), HCV version 3. 0 ELISA (Ortho), VITROS Anti-HCV 6/03/03 Source: CDC. MMWR 2003; 52 (No. RR-3). 13

Repeatedly Reactive Anti HCV Supplementary serological confirmation testing was not performed on this specimen with a high serum to cut-off ration in accordance with CDC guidelines (MMWR, 52 RR 03; 1 -16). Appx 95% of specimens with a high serum to cut-off ratio confirm positive when tested in supplementary tests. The serum to cutoff ratio is not related to severity of disease or acute/chronic phase of infection. Supplementary testing is available only after consultation with Dr. Jeff Massey… 6/03/03 14

Advantages and Impact ? 6/03/03 15

Advantages of Revised Laboratory Guidelines Ø Ø Standard reporting of anti-HCV positive results. Reliable Interpretation of anti-HCV results. Ø Ø 6/03/03 Ensure positive patients receive follow-up Prevent unnecessary evaluation of “false-positives” Low cost of additional testing Better understanding of performance and interpretation 16

Implications Ø Patients and physicians can reliably interpret results Ø Ø Ø 6/03/03 Further clinical evaluation limited to true positives Limit psychological stress on patients who test falsely positive Substantially improve ability to establish public health surveillance systems to monitor effect of prevention and intervention activities 17